This application claims priority of European Patent Application No. 01610036.4 filed Mar. 27, 2001.
The present invention relates to a medical device and, in particular, to an aorta graft device.
An aorta graft is an endovascular prosthesis for placement in aorta in a weakened area, such as at an aneurysm of the abdominal aorta. An aortic aneurysm is an abnormal dilation or enlargement of the arterial wall of the aorta. If the aneurysm is not treated, it can rupture and abruptly cause a fatal blood loss out of aorta into the abdominal or thoracic cavity of patient.
The aorta graft is normally made of a tube of pliable material provided with a stent for anchoring the graft in its intended position within the blood vessel by exerting an outwardly directed radial pressure against the surrounding aortic wall. This requires in the area of the stent a relatively healthy aortic wall that can withstand the radial pressure for years. Patients diagnosed with aortic aneurysms are often in poor health due to other illnesses which increase the risk of complications associated with an operation. Most prior art aorta grafts are for the repair of abdominal aortic aneurysms (AAA) involving the pararenal and infrarenal aorta. Examples of such grafts are described in U.S. Pat. Nos. 5,984,955 and 6,016,810. Many of these grafts are bifurcated and extend into the iliac arteries. Aortic grafts of these types can typically be placed using transluminal, minimally invasive procedures where the graft is percutaneously introduced via a femoral puncture site, and the entire procedure can be performed using local anaesthesia.
With respect to aortic grafts for the repair of thoracoabdominal aortic aneurysms (aneurysms in the descending thoracic aorta) and thoracic aortic aneurysms (aneurysms in the ascending thoracic aorta including the aortic arch) only a few proposals for minimally invasive procedures have been made.
U.S. Pat. No. 6,099,548 proposes to advance the graft into the ascending thoracic aorta and to lock it to the aortic wall by expanding a stent in the proximal end of the graft. However, adjacent the heart the flow rate of blood through aorta is so high that the risk of dislocation of the proximal stent is considerable.
In a particularly lethal kind of aortic aneurysms the aortic wall is dissected to form a bogus lumen that establishes a parallel flow path for blood. The only method of repair is open surgery. In a so-called elephant trunk procedure a stented distal end of a secondary graft part is fixed in the descending aorta, and the proximal end of the secondary graft part is sutured to a primary graft part that is placed in the ascending aorta and anastomosed to the branch arteries carotis communis, subclavia and truncus brachiocephalicus.
During the operation the patient is subjected to cardiac arrest and systemic circulatory arrest, and although the patient has been cooled to a very low body temperature, such as 16xc2x0 C., and selective cerebral perfusion is performed, the duration of the operation is a critical factor.
Dissections of type A where the aortic wall dissection is initiated in the ascending aorta pose a particular problem. With the prior art techniques the mortality is 75% within 24 hours of initiation of the condition and 90% within one week. The surgeon thus has extremely short time to prepare and perform the surgery.
A purpose of the present invention is to improve the efficiency of the surgical repair of implanting the aortic graft device.
With a view to this the aortic graft device according to the invention is characterized in that the primary graft part has an anchoring area positioned between an ascending portion extending to said proximal end and a descending portion extending to said distal opening, that the ascending portion is corrugated, and that the descending portion is at least partially non-corrugated.
The positioning and anchoring of the primary graft part can begin immediately after cardiac arrest has been obtained. The corrugations on the ascending portion of the graft facilitates setting of the ascending portion in a curvature following the path of the ascending aorta in the particular patient. This saves some time. A further major time saving is obtained in that the primary graft part is the first one to be positioned in the patient. After anchoring the primary graft part to the aortic wall, the ascending portion of the graft can be located in the ascending aorta and the descending portion of the primary graft part can be left hanging loose in the descending aorta. Time consuming suturing of the secondary graft part to the primary graft part is avoided which markedly reduces the duration of the critical part of the operation in which cardiac arrest and systemic circulatory arrest are required.
The non-corrugated area on the descending portion makes it possible to connect the descending portion of the graft to a secondary graft part or to the aortic wall at a subsequent operation. When the surgeon has performed the anchoring of the primary graft part he is aware of the time consumed and he can decide to insert a secondary graft part right away if time allows this, or to postpone placement of a secondary graft part or an alternative connection of the distal end of the primary graft part to the aortic wall to another operation. The surgeon also fixes the proximal end of the primary graft part to the desired site of the aortic wall in the ascending aorta.
The anchoring area positioned between the ascending and the descending portions of the primary graft part make it possible for the graft to be fixed to a portion of the aortic wall in vicinity of the three branch arteries on the aortic arch. The anchoring can be made to the distal side of the arteria subclavia at least at the upper portion of the aortic arch and possibly in an annular pattern following the aortic wall.
In an illustrative embodiment, the descending portion of the primary graft part is non-corrugated at least at said first connecting means, and preferably along its full length from said anchoring area to said distal opening. The non-corrugated area makes it easier to obtain a blood tight connection between the primary graft part and the tubular member connected to it.
The descending portion of the primary graft part is provided with at least one stent, and preferably provided with at least two stents, which are located near the anchoring area and at the distal opening, respectively. The stent resiliently acts on the descending portion to keep it open and non-kinking.
In a further embodiment the descending portion of the primary graft has a distal end area which is uncorrugated and unstented and has a length of at least 20 mm. The distal end area can be utilized to couple the primary graft to either a secondary graft or to the aortic wall. It is possible to perform suturing in the distal end area, but it is likewise possible to use the smooth surface character in the distal end area to obtain a pressure-tight sealing between the primary graft and the secondary graft.
The descending portion of the primary graft part is preferably supported by a stent at least along the majority of its length. By stenting, the descending portion is kept fully open, also when it is subjected to compressing or kinking actions on the exterior of the descending portion which is hanging freely floating in the aortic vessel downstream of the anchoring area. This is particularly useful when a secondary graft part is to be connected to the primary graft part at separate surgery.
In order to facilitate handling and placement of the primary graft at least the ascending portion of the primary graft part is precurved. The precurved shape reduces the size of bending forces required to keep the ascending portion in position during suturing of the anchoring area and thus minimizes the time spent on correcting the location of the primary graft part during suturing.
In a preferred embodiment, a wedge-shaped area of graft side wall in the ascending portion has been removed and the exposed opposite rim areas have been joined to each other. The removal of the wedge-shaped area results in a distinct or sharp bend in the graft part at the place of the removed material and allows on the one hand manufacturing of the graft part as a straight tubular part with uniform properties and on the other hand the more sharp bend can be obtained in a comparatively easy manner.
It is preferred that the ascending portion has a length in the range of from 11 to 17 cm, that said descending portion has a stented length in the range of from 5 to 10 cm, and that said distal end area has a length in the range of from 2 to 3 cm. These features make the primary graft part quite flexible in the rather long corrugated ascending portion and well suited to accept different kinds of fixation modes in the descending portion, such as fixation to a secondary graft part which is fixed to the natural aortic wall, or fixation of the descending portion directly to the natural aortic wall.
When a patient is suffering from a dissection of type A, the development of the dissection and the paths it follows can be somewhat unpredictable, and in order to be more certain that every part of the dissection is blocked at a particular location in the aorta, the anchoring area can comprise an annular area encircling the primary graft part. This allows for a fixation of the graft to the aortic wall along a full circumference of the wall.
It is preferred that said annular area is uncorrugated and unstented and has a length of at least 10 mm. The surgeon can quickly fix this annular anchoring area to the aortic wall because the area is free from pre-manufactured corrugations and stents and has a length that provides easy access to a contact point between graft and wall when the suture is to be applied.
The anchoring area can in an embodiment include a lateral area which extends away from the annular area in direction of the ascending portion. This lateral area can be positioned next to the three branch arteries and quickly be fixed to the aortic wall.
In a further development of the latter embodiment the lateral area is carrying a marking, such as a coloring distinct from the remainder of the primary graft part. The coloring makes it very easy and thus quick for the surgeon to position the primary graft part with the lateral area facing correctly in the cranial direction.
In yet a further development the lateral area includes a lateral opening so that the surgeon does not spend additional time for providing communication between the aorta vascular space inside the graft and the aortic branch arteries.
The primary graft part can be supplied in or be set into a mounting state where the ascending portion has been everted into said descending portion to present said annular anchoring area as a rim area to be sutured to the aortic wall.
A dissection of type A can extend into the area of the heart valve and depending on the actual circumstances, such as whether a coronary artery is involved in the dissection, it can be insufficient to repair only the aorta. If additional surgery is required on the heart valve, the graft device preferably also includes an end portion with a heart valve.
When the graft device includes a heart valve it is preferred that the primary graft part has a proximal opening, and that the end portion with the heart valve is a separate part to be fixed to said primary graft part at said proximal opening. This division of the graft device allows the surgeon to split the surgery into separate rounds where the time consuming fixation of the end portion to the heart and coronary arteries can be performed while the circulatory system is functioning by a cardio-pulmonary bypass and appropriate cannulations. Then, in a second round, the primary graft part can be applied after establishing systemic circulatory arrest, but the duration of circulatory arrest is considerably shortened by performing a large part of the surgery required during said first round.
As mentioned above, the descending portion of the primary graft part can be connected to the aortic wall in different manners. In one embodiment, the graft device includes a secondary graft part with a second connecting means that by engagement with said first connecting means connects said secondary graft part to said primary graft part. Use of the secondary graft part can often be a preferred alternative to suturing of the descending portion to the aortic wall. The second connecting means makes possible a quick establishment of the interconnection between the parts.
This embodiment can be further developed so that the engagement involves geometrically interlocking parts on said first and second connecting means, respectively, preferably so that the engagement is enhanced when said secondary graft part is pulled in the distal direction. The geometrical locking of the two parts can provide better long term durability of the graft device which continuously is subjected to the pressure pulses produced by the heart beats.